A study led by Johan Elf (Uppsala University/SciLifeLab) have demonstrated how the Cas9 component of the CRISPR-Cas9 genome editing technology is able to find the right DNA sequence. The results are published in Science magazine.

The CRISPR-Cas9 system has revolutionised biological research as it enables correcting or modifying essentially any DNA sequence. The hope is that these genetic scissors will make it possible for genetic diseases to be cured and prevented.

Cas9 is that the molecule can be programmed with a piece of chosen RNA, which can then be made to seek out the corresponding sequence in the genome. Johan Elf and his team have now discovered how fast Cas9 finds the right sequence as it unwinds the DNA double helix to test for correct base pairing to the guide RNA. This mechanism is uncommon compared to other proteins that search DNA code, which generally only try to recognise a specific sequence by sensing the outside of the DNA double helix. The researchers demonstrate that the price Cas9 pays for its flexibility is time. To find the target faster, more Cas9 molecules searching for the same DNA sequence are required.

SciLifeLab has been created by the coordinated effort of four universities in Stockholm and Uppsala: Stockholm University, Karolinska Institutet, KTH Royal Institute of Technology and Uppsala University.